ubcctf/instanced

NOTE: this was written for maplectf 2023, while it is functional, it is not ready for use out of the box.

Manages challenge instances on-demand.

instanced runs in the k8s cluster and exposes an HTTP API which is used to request instances. Challenge templates are added in the form of CRDs or config. Example format is in this repository. instanced must be restarted every time new CRDs are applied.

Instances created are kept track of in a local sqlite database. The instancer periodically scans the database for expired instances and deletes them.

Instancer CLI tool

The instancer cli tool has been installed to the bastion.

maple@bastion:~$ instances
Instancer Admin CLI

Syntax: instances COMMAND [params]
Commands:
  help                                Print this help.
  list                                list all active instances.
  chals                               Show available challenges.
  chals  [CTFD TEAM ID]               Show challenge statuses for a team.
  create [CTFD TEAM ID] [CHAL KEY]    create a new challenge instance.
  delete [INSTANCE ID]                delete an instance.
  purge                               purge all instances.

API

• GET /instances - get list of active instances
• GET /challenges - get available challenge types
• GET /challenges?team=$ID - get list of available challenges and instance states for specific team
• POST /instances?chal=$CHALLNAME&team=$ID - provision an instance for specific challenge and team
• DELETE /instances?id=$ID - delete challenge with id
• DELETE /instances - delete all challenges

sequenceDiagram
    actor User
    participant CTFd
    participant instanced
    participant k as kube-apiserver
    User->>CTFd: Load Instances Page
    CTFd->>instanced: GET /challenges?team=ID
    instanced->>CTFd: [{expiry, name, url}, ...]
    User->>CTFd: Restart Instance
    CTFd->>instanced: POST /instances?chal=CHALLNAME&team=ID
    instanced--)k: Create Objects
    instanced->>CTFd: URL of new instance
    CTFd->>User: Instance Created
    Note over instanced: Instance expires
    instanced--)k: Destroy Objects

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